The government has told businesses frictionless trade with the EU will end this year with the introduction of import checks at the UK border.
EU trade will not be waved through with zero checks which had been the plan under a no-deal Brexit and traders will not be able to use special arrangements to lodge new paperwork after a grace period at a later date.
Officials said firms will have enough notice to prepare for changes in time for 1 January.
Cabinet Minister Michael Gove told attendees at a Border Delivery Group event: "The UK will be outside the single market and outside the customs union, so we will have to be ready for the customs procedures and regulatory checks that will inevitably follow."
From next January, all traders will have to submit customs declarations and be liable to goods' checks for customs, regulatory standards and food safety on cross channel ferries, for example.
These facilities, as well as the Channel Tunnel, have been designed for minimal border checks.
In order to function, new customs infrastructure, facilities and systems as well as staff, agents and vets will have to be in place by the end of this year.
It was quietly confirmed in a speech. Some might argue it has been inevitable since the election. But the change in the way the UK trade border functions with our biggest trade partner is one of the single biggest changes to the way the UK economy functions.
Put simply, many industries rely on the frictionless free flow of goods between the UK and the continent. The unequivocal message from Michael Gove is that businesses should prepare for the the end of that as 2020 draws to a close.
Whereas the impact of all this in the Irish Sea has garnered considerable attention, the new trading arrangements between Dover and Calais and along the Channel Tunnel, will have a bigger effect on the economy.
By getting businesses to take the prospect seriously, the government's hope is that more will be prepared and so delays and disruption can be limited.
Businesses will not get the grace period for dealing with customs forms, offered as part of no deal planning. But we are dealing with parts of the border that are designed too run without checks.
The government's seriousness of purpose here will also need to be demonstrated in the employment of customs officers, help training thousands more customs agents, mass recruitment of vets, and in diggers in the ground constructing new customs posts.
But almost every independent economic analysis - and the government's own until now - has shown that such extra trade friction through the recreation of "non-tariff barriers" with what is currently our biggest market, will be an overall hit to the economy.
Preparation can help alleviate some of that hit, but not all.
"Government will need to move fast if it intends to provide the necessary infrastructure to carry out full border controls on imported goods from January 2021, " said Andrew Opie, the British Retail Consortium's director of food and sustainability.
"Without the necessary infrastructure up and running from day one, consumers in the UK will see significant disruption, particularly in the availability of fresh fruit and vegetables."
Industries from car manufacturers to food distributors which rely on the frictionless free flow of goods with the continent say they face extra costs, delays and red tape from what are known as non-tariff barriers.
If no trade deal is reached with the EU, taxes such as tariffs will also need to be charged and collected.
Mr Gove also told the conference there would be light touch administration of trade across the Irish Sea.
But last week it emerged that Stena Line, the biggest operator of ferries in the Irish Sea, is preparing for trade checks between Great Britain and Northern Ireland.
Source: BBC News